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1.
Recently, processes combining an electrical field as a driving force to porous membranes have been developed for the separation of protein or peptide mixtures to obtain more purified products with higher functionality or nutritional value. The objective of this work was to evaluate the influence of the flow rate on the productivity and selectivity as well as on the electrodialytic parameters of electrodialysis with an ultrafiltration membrane (EDUF) during the fractionation of peptides from a beta-lactoglobulin tryptic hydrolysate. It appeared that the feed solution flow rate had no impact on the yield of the process but induced changes in the selectivity. In fact, increases in the flow rate decreased the migration of the peptides with limited electrophoretic mobility.  相似文献   

2.
Hydrophobicity of bitter peptides from soy protein hydrolysates   总被引：6，自引：0，他引：6  
Soy peptides were characterized for flavor, chemical properties, and hydrophobicity to investigate their relationships with bitterness. Five peptide fractions ranging in average molecular mass from 580 to 11300 Da were fractionated by ultrafiltration from two commercial soy protein hydrolysates. The bitterness of fractionated peptides was related to molecular mass, with maximum bitterness observed at approximately 4000 Da for one hydrolysate and 2000 Da for the other. The bitterness increased as the peptide M(w) decreased to 3000 Da for the first hydrolysate and to 2000 Da for the second one and then decreased as the peptide M(w) decreased below 1000 Da. The peptide fraction with molecular mass of <1000 Da showed the lowest bitterness for both. The hydrophobicity data based on Q values do not support Ney's Q rule as a predictor of bitterness for soy peptides.  相似文献   

3.
The in vitro angiotensin I-converting enyzme (ACE) inhibitory activity of Pacific hake hydrolysates was investigated as a function of hydrolysis conditions, starting material variability, and ultrafiltration. Hake fillets were hydrolyzed using Protamex protease under various conditions of pH, hydrolysis time, and enzyme-to-substrate ratio (% E/S) according to a response surface methodology (RSM) central composite design. The hydrolysate produced at pH 6.5, 125 min, and 3.0% E/S had an IC 50 of 165 +/- 9 microg of total solids/mL. ACE-inhibitory activity was not significantly different (P < 0.05) for hydrolysates produced using higher time-enzyme combinations within the model or from fish of different catches. Ultrafiltration (10 kDa molecular mass cutoff) resulted in an IC50 value of 44 +/- 7 microg of peptides/mL, 2.5 times more potent than the commercial product PeptACE Peptides (IC50 = 114 +/- 8 microg of peptides/mL). These results suggest that hydrolysates prepared with minimal fractionation from Pacific hake, an undervalued fish, may be a commercially competitive source of ACE-inhibitory peptides.  相似文献   

4.
The squid (Loligo pealei) byproduct composed of heads, viscera, skin, fins, and small tubes was subjected to hydrolysis at 55 degrees C and natural pH (6.8) using endogenous proteases. Squid hydrolysate was characterized during the course of hydrolysis for changes in the degree of hydrolysis, viscosity, electrophoretic pattern of proteins and peptides, and amino acid and fatty acid profiles. The change in viscosity can be used to monitor the progress of protein hydrolysis up to the molecular mass of 26.63 kDa. The 2 h hydrolysis resulted in a 2-fold increase in the total free amino acids and yielded hydrolysate with protein molecular mass of < or =45 kDa having feed attractability and good amino acid and fatty acid profiles with high contents of essential amino acids and fatty acids. Such hydrolysis-induced changes can make squid byproduct hydrolysate a good source of aquaculture feed ingredient, especially for a starter diet for larval fish.  相似文献   

5.
The dipeptidyl-peptidase IV (DPP-IV)-inhibitory activity of peptides derived from Atlantic salmon skin gelatin hydrolyzed by alcalase (ALA), bromelain (BRO), and Flavourzyme (FLA) was determined. The FLA hydrolysate with the enzyme/substrate ratio of 6% showed the greatest DPP-IV-inhibitory activity. The hydrolysate was fractionated by ultrafiltration with 1 and 2.5 kDa cutoff membranes, and the <1 kDa fraction had the highest DPP-IV-inhibitory activity with an IC(50) value of 1.35 mg/mL. The F-1 fraction further isolated by HPLC showed the IC(50) value against DPP-IV of 57.3 μg/mL, and the peptide sequences were identified as Gly-Pro-Ala-Glu (372.4 Da) and Gly-Pro-Gly-Ala (300.4 Da). The synthetic peptides showed dose-dependent inhibition effects on DPP-IV with IC(50) values of 49.6 and 41.9 μM, respectively. The results suggest that the peptides derived from Atlantic salmon skin gelatin would be beneficial ingredients for functional foods or pharmaceuticals against type 2 diabetes.  相似文献   

6.
Hoki (Johnius belengerii) skin gelatin was hydrolyzed with three commercial enzymes to identify radical-scavenging potencies of derived peptides. Peptides derived from tryptic hydrolysate exhibited the highest scavenging activities on superoxide, carbon-centered 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals assessed by ESR spectroscopy. Following consecutive chromatographic separations of tryptic hydroolysate, the peptide sequence His-Gly-Pro-Leu-Gly-Pro-Leu (797 Da) acted as a strong radical scavenger under studied conditions. Further, this peptide could act as an antioxidant against linoleic acid peroxidation and the activity was closer to the highly active synthetic antioxidant butylated hydroxytoluene (BHT). In addition, antioxidative enzyme levels in cultured human hepatoma cells were increased in the presence of this peptide and it was presumed to be the peptide involved in maintaining the redox balance in the cell environment. Present data indicate that free-radical-scavenging activities of hoki skin gelatin peptides substantially contribute to their antioxidant properties measured in different oxidative systems.  相似文献   

7.
Solutions of tryptic hydrolysate of bovine beta-lactoglobulin were fractionated by liquid-phase IEF in a preparative Rotofor cell at constant power for 2 h without ampholytes in order to identify interactions between peptides. The 20 peptide fractions collected were analyzed by capillary electrophoresis and SDS-PAGE under native, denaturing, and reducing conditions. The hydrolysate was shown to be composed mainly of acidic peptides (pI 2-5, 62%) of molecular mass below 6 kDa, and numerous disulfide bonds were detected. Purified peptides (beta-LG 15-20, 71-75, 76-82, and 84-91) were also focused individually and in mixtures and matched to components of the IEF fractions obtained from the tryptic hydrolysate of beta-LG. The separation of acidic (beta-LG 84-91) and basic (beta-LG 76-82) peptides was achieved by IEF, whereas uncharged peptides (beta-LG 15-20 and 71-75) were poorly separated due to their low electrophoretic mobility. Because no peptide-peptide interaction could be identified by IEF fractionation, it is suggested that electrical fields may decrease electrostatic interactions between charged peptides.  相似文献   

8.
Elastin hydrolysate has apparent beneficial effects, and the food-derived peptide prolyl-glycine (Pro-Gly) is present in human blood after oral ingestion. Following ingestion of elastin hydrolysate (10 g/60 kg body weight) by healthy human volunteers, peripheral blood was used to prepare plasma samples from which peptides were extracted by solid phase extraction and fractionated by size-exclusion chromatography (SEC). Peptides in the SEC fractions were derivatized with phenyl isothiocyanate (PITC) and resolved by reversed phase (RP)-HPLC. Pro-Gly was the major food-derived elastin peptide, reaching a maximum (18 μM) at 30 min after ingestion, and decreasing to approximately 20% at 4 h after ingestion. Finally, in cell culture, levels of Pro-Gly in the medium above 0.1 μg/mL significantly enhanced elastin synthesis of normal human dermal fibroblasts (NHDF) without affecting the rate of cell proliferation.  相似文献   

9.
The purpose of this research was to study the effect of centrifugal ultrafiltration (UF) on the composition of aqueous extracts of saffron spice. The contents of seven crocetin esters, picrocrocin, and two kaempferol glycosides were analyzed by UV-vis and HPLC in the filtrate and retentate fractions from 16 centrifugal filter devices with regenerated cellulose (RC) and polyethersulfone (PES) membranes ranging from 1-100 kDa nominal molecular weight cutoff (MWCO). The separation of crocetin esters from picrocrocin and their concentration with centrifugal UF have been demonstrated. A great heterogeneity of results regarding devices with equal MWCO was found that could not be related to the membrane material or manufacturer. Four devices of 5 and 10 kDa MWCO, three of which had RC membranes, showed the best results. The device having the lowest MWCO also showed a potential to obtain picrocrocin without crocetin esters and could be considered in successive UF steps. The less polar crocetin esters were rejected better than the others.  相似文献   

10.
Fish protein hydrolysate (FPH) produced by incubation of Pacific hake fillet with 3.00% Protamex at pH 6.5 and 40 degrees C for 125 min demonstrated in vitro ACE-inhibitory activity (IC50 = 165 microg/mL), which was enhanced by ultrafiltration through a 10 kDa molecular weight cutoff membrane (IC50 = 44 microg/mL). However, after simulated gastrointestinal digestion, FPH and ultrafiltrate had similar ACE-inhibitory activity (IC 50 = 90 microg/mL), indicating that FPH peptides act as "pro-drug type" inhibitors and that enrichment by ultrafiltration may be unnecessary. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry confirmed that the molecular weights of major peaks were <1 kDa regardless of ultrafiltration. ACE-inhibitory activities of digested hydrolysates were not significantly affected by preincubation with ACE ( P > 0.05) and exhibited a competitive inhibitory mode. A permeability assay using fully differentiated colorectal adenocarcinoma (Caco-2) cells showed an apical to basolateral transport of peptides that ranged from approximately 2 to 20% after 2 h at 37 degrees C. Pacific hake fillet hydrolysates are a potentially bioavailable source of ACE-inhibitory peptides awaiting further in vivo study.  相似文献   

11.
The nitrogen composition of wines aged with yeast for a long period of time, as in the case of sparkling wines, depends on the composition of the base wine and on the compounds released by the yeast. In this paper, the release of the different classes of nitrogen compounds during autolysis of one of the strains of yeast used in the manufacture of sparkling wines has been studied. The yeast, Saccharomyces bayanus, was suspended in a model wine buffer, pH 3.0 and 10% ethanol, and incubated at 30 degrees C. Samples of the autolysate were taken after 4, 24, 48, 72, 168, and 360 h of autolysis. An electrophoretic and chromatographic study was conducted of the proteins, peptides with molecular weights higher and lower than 700 Da, and amino acids released during the autolysis. Using SDS-PAGE, it was observed that it was predominantly polypeptides with molecular weights lower than 10 000 that were released. Through HPLC of the fraction lower than 10 000 Da, it was observed that it is polypeptides with molecular weights of between 10 000 and 700 Da that are released first and that these later break up to give rise to peptides with molecular weights lower than 700 Da, which in turn break down into amino acids. This indicates that the nature of the nitrogen compounds present in wines aged with yeast depends on the aging time, being less polymerized as the aging time increases.  相似文献   

12.
Peptides derived from soybean beta-conglycinin and pork protein stimulate cholecystokinin (CCK) secretion from the enteroendocrine cells (EECs) and suppress food intake. Here we examined CCK-releasing activities from the enteroendocrine cell line STC-1, in peptides derived from underutilized legumes, and found much higher activity in the peptic hydrolysate of Country beans (CBP) compared to that from other legume-derived peptides including beta-conglycinin peptone. Active components in CBP were separated into acetonitrile-soluble fractions, but the activities were abolished after pronase treatment. To identify the Country bean protein containing the active peptides, Country bean protein extracts in an alkaline solution (CBE) were fractionated based on isoelectric point or molecular weight. Peptones prepared from CBE fractions containing a 51 kDa major protein stimulated CCK release, but other fractions did not. N-Terminal sequence analysis indicated that the 51 kDa protein is a phaseolin-like globular protein, and we designated this protein dolicholin. These results indicate that Country bean-derived peptides are very potent legume peptides in stimulating CCK secretion from EECs and that the stimulant peptides originate from dolicholin, a newly identified phaseolin-like globular protein in Country beans.  相似文献   

13.
The inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate produced by papain action was studied. The ice crystal growth was monitored by thermal cycling between -14 and -12 degrees C at a rate of one cycle per 3 min. It is shown that the hydrolysate fraction containing peptides in the molecular weight range of about 2000-5000 Da exhibited the highest inhibitory activity on ice crystal growth in ice cream mix, whereas fractions containing peptides greater than 7000 Da did not inhibit ice crystal growth. The size distribution of gelatin peptides formed in the hydrolysate was influenced by the pH of hydrolysis. The optimum hydrolysis conditions for producing peptides with maximum ice crystal growth inhibitory activity was pH 7 at 37 degrees C for 10 min at a papain to gelatin ratio of 1:100. However, this may depend on the type and source of gelatin. The possible mechanism of ice crystal growth inhibition by peptides from gelatin is discussed. Molecular modeling of model gelatin peptides revealed that they form an oxygen triad plane at the C-terminus with oxygen-oxygen distances similar to those found in ice nuclei. Binding of this oxygen triad plane to the prism face of ice nuclei via hydrogen bonding appears to be the mechanism by which gelatin hydrolysate might be inhibiting ice crystal growth in ice cream mix.  相似文献   

14.
A simplified and rapid procedure for the determination of pyroglutamic acid in peptides was developed. The method involves the enzymatic cleavage of an N-terminal pyroglutamate residue using a thermostable pyroglutamate aminopeptidase and isocratic HPLC separation of the resulting enzymatic hydrolysate using a column switching technique. Pyroglutamate aminopeptidase from a thermophilic archaebacteria, Pyrococcus furiosus, cleaves N-terminal pyroglutamic acid residue independent of the molecular weight of the substrate. It cleaves more than 85% of pyroglutamate from peptides whose molecular weight ranges from 362.4 to 4599.4 Da. Thus, a new method is presented that quantitatively estimates N-terminal pyroglutamic acid residue in peptides.  相似文献   

15.
Volatile and nonvolatile compounds present in the water-soluble fraction (WSF) and water-soluble fraction with molecular weight lower than 1000 Da (WSF < 1000 Da) of six Spanish cheeses, Cabrales, Idiazábal, Mahón, Manchego, Roncal, and a goat's milk cheese, were analyzed. Different nitrogen fractions (determined by Kjeldahl method), caseins (by capillary electrophoresis), peptides and amino acids (by HPLC), and volatile components (by dynamic headspace coupled to GC-MS) as well as mineral content in the cheese fractions were analyzed and compared. The different nitrogen and volatile compounds identified in the WSF were characteristic of each cheese variety. Cabrales cheese displayed the highest content of free amino acids and the highest quantity and variety of volatile compounds. The WSF < 1000 Da fraction was less representative, especially for volatile compounds, as some of the components were lost in the ultrafiltration. Alcohols were better recovered than ketones and esters.  相似文献   

16.
Purification of lactoferricin (Lfcin), a cationic antimicrobial peptide, was achieved by peptic digestion of food grade bovine lactoferrin (LF) followed by fractionation on an industrial grade cation exchange resin with stepwise salt gradient elution. The digest and eluted fractions were partially characterized by MALDI-ToF MS and N-terminal sequencing. A fraction eluted using phosphate buffer with 2.0 M NaCl contained predominantly two peptides with masses of 3196 and 3124 Da, which corresponded to the 26- and 25-amino acid peptides FKCRR WQWRM KKLGA PSITC VRRAF (A), containing the Lfcin sequence. Putative sequences of cationic peptides in other eluted fractions included FKNKS RSFQ, WRMKK LGAPS ITCVR RA, and GAPSI TCVRR AFALE CIRAI AEKKA. The iron saturation level of LF had no effect on the production of Lfcin. Nevertheless, the digestion of LF containing lower iron content led to the production of a higher quantity of low molecular weight cationic peptides. A two-step process using industrial grade cation exchange resin led to 35% recovery of Lfcin and also produced other cationic peptides with potential bioactive properties.  相似文献   

17.
Summary Low molecular weight fractions (LMW; <5000 daltons) of organic matter were isolated from three soils by a mild extraction procedure and gel-permeation chromatography. The peptides present in the LMW soil extracts were separated on a Whatman Partisphere C18 and a Beckman Ultrapore C8 column by reverse-phase high performance liquid chromatography (HPLC). The peptide fractions were collected, acid hydrolyzed, and analyzed for amino acid composition. The C8 bonded-phase column gave better separation of the LMW soil peptide material than the C18 column. The total quantities of amino acids released from LMW peptides by acid hydrolysis were greater than the quantities released by immobilized protease hydrolysis (Warman and Isnor 1990). Total soil N present in the form of LMW peptides in these three soils ranged from 4 to 15%. The total recovery of peptide amino acid-N showed little difference between the C18 and C8 columns for two of the soils tested.  相似文献   

18.
In this study, collagen extracted from chicken legs (which are the yellow keratin parts containing a nail) was hydrolyzed with various enzymes, and the angiotensin I-converting enzyme (ACE)-inhibitory activity of each hydrolysate was determined. The hydrolysate by treatment with an Aspergillus species-derived enzyme had the highest activity (IC 50 = 260 microg/mL). The fraction of this hydrolysate obtained by ultrafiltration with a molecular-weight cutoff of 3000 Da (low fraction) had a stronger activity (IC 50 = 130 microg/mL) than the fractionated one. This fraction was further fractionated by HPLC, and the peptides in the fraction with high ACE-inhibitory activity were identified. The amino acid sequences of the four peptides were identified using a protein sequencer. These peptides were synthesized to confirm their ACE-inhibitory activities; this showed that peptides with a Gly-Ala-Hyp-Gly-Leu-Hyp-Gly-Pro sequence had the highest activity (IC 50 = 29 microM). When the low fraction was administered to spontaneous hypertensive rats, a decrease in their blood pressure was observed after 2 h of administration, and a significant decrease in blood pressure (-50 mmHg) was observed after 6 h. Moreover, long-term administration studies indicated that the low fraction showed a significant suppression of increased blood pressure.  相似文献   

19.
Gelatin was extracted from the skin of Japanese flounder ( Palatichtys olivaceus ) and was subjected to enzymatic hydrolysis. The peptic hydrolysate resulted in a potent antioxidative peptide Gly-Gly-Phe-Asp-Met-Gly (582 Da), which bears +12.61 kcal/mol hydrophobicity. The antioxidative potential of the peptide was characterized by analyzing the protective effect of the peptide on reactive oxygen species (ROS)-mediated intracellular macromolecule damage. It was found that the peptide is a potent scavenger of intracellular ROS, thereby protecting the radical-mediated damage of membrane lipids, proteins, and DNA. Moreover, the peptide is capable of upregulating the expression of inherent antioxidative enzymes, superoxide dismutase-1, glutathione, and catalase. Collectively, it can be concluded that Japanese flounder skin, a processing byproduct of filleting, can be effectively used to produce a bioactive peptide with potent antioxidant capacity.  相似文献   

20.
This work was aimed at the isolation, purification, and characterization of novel antimicrobial peptides from chicken egg white lysozyme hydrolysate, obtained by peptic digestion and subsequent tryptic digestion. The hydrolysate was composed of over 20 small peptides of less than 1000 Da, and had no enzymatic activity. The water-soluble peptide mixture showed bacteriostatic activity against Gram-positive bacteria (Staphylococcus aureus 23-394) and Gram-negative bacteria (Escherichia coli K-12). Two bacteriostatic peptides were purified and sequenced. One peptide, with the sequence Ile-Val-Ser-Asp-Gly-Asp-Gly-Met-Asn-Ala-Trp, inhibited Gram-negative bacteria E. coli K-12 and corresponded to amino acid residues 98-108, which are located in the middle part of the helix-loop-helix. Another novel antimicrobial peptide inhibited S. aureus 23-394 and was determined to have the sequence His-Gly-Leu-Asp-Asn-Tyr-Arg, corresponding to amino acid residues 15-21 of lysozyme. These peptides broadened the antimicrobial activity of lysozyme to include Gram-negative bacteria. The results obtained in this study indicate that lysozyme possesses nonenzymatic bacteriostatic domains in its primary sequence and they are released by proteolytic hydrolysis.  相似文献   

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